Sorry, but the game is already frozen for final Version 0.9, so this downgrade feature unfortunately could make it in time.yv0751, may I have a request? I'm in the new ending already, and it's quite frustrating to have to gather the silver nails again, even though I have 20+ golden ones already. Please make it possible to split the golden nails into silver (at a loss, of course, like 1 -> 5, 1 -> 3, or even 1 -> 1), maybe with some gem sacrifice to make it work as a recipe. Or, alternatively, make it possible to use golden nails in place of silvers.
There's no problem with wood or metal bars, you never need anything below top level (gold / ebony). Not many, anyway...
Going to the shop should give enough after two or three days. Also Nyx finds some.
You could also console command it in the worst case.